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The transparent chip inside a vintage Hewlett-Packard floppy drive
- kens 3y agoAuthor here if anyone has questions. A bit of a change from my usual x86 chips...
- e3a8 3y agoWonderful work! Your articles are my favorite coffee reads
- myself248 3y ago> Inconveniently, metal that contacts silicon, metal that crosses over silicon, and metal that forms a transistor all appear very similar in this chip. This makes it more difficult to determine the wiring. I've heard that all diodes are LEDs, if one's vision extends to the infrared. Is it possible to fire up the chip and photograph it in the infrared, and would that make the transistors stand out?
- KRAKRISMOTT 3y agoHigh resolution thermal imaging is tightly regulated
- philipkglass 3y agoThe emission from silicon referred to by myself248 is in the near infrared, not the thermal range. It's a commonly used diagnostic technique for silicon solar cells: https://www.pveducation.org/pvcdrom/characterisation/electroluminescence https://www.pveducation.org/pvcdrom/characterisation/electro... I don't know if it could be used for the much smaller features found on integrated circuits, though.
- gorkish 3y agoAs the restrictions are now blocking the IMPORT of such equipment it really is getting to be quite a joke. In the US we are only allowed to have expensive potato quality cameras with 9fps and even then that's not shitty enough -- they also have to have to inject artificial noise into it!
- lightedman 3y agoThermal is not the same as near-red IR, which is what is being discussed here.
- acuozzo 3y agoWhy?
- voakbasda 3y agoBecause the government knows IR would be a pivotal tool in a civilian guerrilla uprising, and they want to keep such things out of the hands of the proletariat?
- acuozzo 3y agoGot it. It was a genuine question asked out of ignorance on my part. How would the extra resolution be useful in warfare?
- KRAKRISMOTT 3y agoAnti aircraft missiles (everything from plane launched to manpads), heat seeking weaponry capabilities, night vision, multispectrum sensors, optical gas imaging and a whole host of other dual use scientific applications. High resolution thermal vision is the lynchpin behind all of them. I am not sure why they are still tightly controlled since you can easily acquire them overseas.
- voakbasda 3y agoThe US government is terrified of its citizenry, as they are the only people that stand a chance of “fixing” it.
- kens 3y agoWell, John McMaster was able to do some IR imaging of a chip: https://hackaday.com/2019/06/20/seeing-transistors-switch-in-infrared/ https://hackaday.com/2019/06/20/seeing-transistors-switch-in... But in this case, I think it's easier to squint at the die to distinguish the features by subtle differences in color. It's possible to tell them apart, but I wasted a lot of time before realizing "Oh, that's a transistor‽"
- doubled112 3y agoI've been successful at making many electronic parts light emitters even when they're not designed to be. Some last longer than others under the conditions.
- userbinator 3y agoSince you mention it was a defective part, were you able to see the defect on the die?
- kens 3y agoWe didn't see anything obviously wrong with the part. One bit of communication with the microprocessor was flaky, so it was probably a weak transistor. The consequence was that the Z80 attempted to look up a command in a lookup table, but the command wasn't there so it ended up looping through all of memory, hanging the floppy drive.
- paulrpotts 3y agoI'm not informed enough to come up with a good question, but I love your work! And I love the concept of chips built on sapphire, even if it didn't win in the marketplace. Could we get Ruby running on ruby? :P
- blacksmith_tb 3y agoRuby (the gemstone) is just a red sapphire, in fact[1]. So maybe? 1: https://geology.com/gemstones/ruby-and-sapphire/ https://geology.com/gemstones/ruby-and-sapphire/
- topspin 3y agoYou mentioned that SOS still has a niche. What examples of current RF devices are using SOS?
- kens 3y agoPeregrine Semiconductor makes various SOS products. Here's a random example, an RF digital attenuator: https://www.psemi.com/pdf/datasheets/pe43205ds.pdf https://www.psemi.com/pdf/datasheets/pe43205ds.pdf
- o11c 3y agoThoughts on distinguishing similar-looking things: * take multiple pictures from slightly different angles * take pictures using sensors for different frequencies (can be done with a colored transparent sheet, though simply using different cameras will have some effect) * shine light from different angles * shine different frequencies of light at it
- Aloha 3y agoIs a modern yield for SOS still as low as quoted?
- kens 3y agoI don't have figures for modern yields. I hope the yield is better. But I think there are fundamental difficulties with matching up the sapphire and silicon crystals that tends to produce faults.
- Aloha 3y agoI'm astounded HP made commercial products out of a process with such a low yield, I dont know how that was economical. (though none of the HP gear was exactly low margin)
- kens 3y agoThe HP Journal article mentions the 9% yield as if they are perfectly fine with it. They were building these chips internally for high-margin gear (as you said), so it probably didn't matter if the chip cost $10 or $100, as long as it has the performance that they need. It's a completely different market from microprocessors such as the 6502 or the 8086, where customers are looking closely at the cost of the chip.
- Aloha 3y agoand RF components are still in that space to a greater or lesser extent too.
- morsch 3y ago> I'm not sure what the oval stamp at the top is, maybe a turtle? It's a teapot, on its head. How odd!
- lelandfe 3y agoPerhaps https://en.m.wikipedia.org/wiki/Utah_teapot https://en.m.wikipedia.org/wiki/Utah_teapot
- anonymousiam 3y agoI spent a few weeks at the HP Cupertino facility in 1982, and got a tour of their chip and computer production facilities too. They were very proud of their SoS (Silicon On Sapphire) technology, which was fairly new at the time. I think they moved all the chip production to Singapore shortly thereafter. https://www.hpmuseum.net/divisions.php?did=2 https://www.hpmuseum.net/divisions.php?did=2 https://venturebeat.com/business/hp-shutting-its-cupertino-campuses-and-moving-employees-to-palo-alto-internal-memo/ https://venturebeat.com/business/hp-shutting-its-cupertino-c...
- RandomBK 3y ago> HP achieved a yield of 9%, meaning 91% of the dies failed. This line really stood out to me - I was aware early semi yields were poor, but this poor? Was this par-for-the-course for technology at that time, or was this bad even by 70s standards? What do typical yield numbers look like today?
- deleted 3y ago[deleted]
- gary_0 3y agoI recall reading that a brand new cutting-edge process node might get 60% yield, but a completely mature node is circa 90% (if memory serves). Yields for a new process usually go up over time as manufacturing bugs are worked out.
- Baldbvrhunter 3y agoIsn't that survivorship bias? Processes that never improve yield are abandoned
- kragen 3y agono, it's just what happens with any process; as you gain more experience with it, you learn more about it, so you can get more and more controlled results
- gary_0 3y agoYes, and companies like TSMC and Intel probably have vast internal documentation about where and how their processes can improve yield as they run their newest fabs. The research required to implement a new process can take decades to get to the mass-production stage. Given the billion of dollars at stake and thousands of human-years of R&D needed, none of these companies are "winging it" and their scientists and engineers know how to plan ahead to the best of their considerable abilities. For a glimpse at how they do things, see this fascinating talk: https://www.youtube.com/watch?v=NGFhc8R_uO4 https://www.youtube.com/watch?v=NGFhc8R_uO4
- qwezxcrty 3y agoIt may worth mentioning the modern successor of the SOS technology is SOI. A thin film of crystaline silicon insulated from the bulk by a thin film of SiO2 is used for fabrication of the circuits.
- kazinator 3y ago> Since the sapphire substrate is an insulator, transistors are completely isolated, unlike a regular integrated circuit. This reduces the capacitance between transistors, improving performance. That sounds like it would be very good for analog, like op-amps.
- pjc50 3y agoSomeone mentioned Peregrine; here's a presentation from them on SoS and why they're using it for RF: https://www.psemi.com/newsroom/blogs/15645-part-5-why-silicon-on-sapphire https://www.psemi.com/newsroom/blogs/15645-part-5-why-silico...
- GaryHak 3y agoDon’t tell the audiophiles. SOS-preamp here we come!
- RecycledEle 3y agoI wish I could find a sample of a transparent (silicon of sapphire) chip to hang on the wall, maybe with a magnifying glass nearby. I checked eBay, but did not see any.